The increase in human population is forcing industrial development which is inherently associated with the drawbacks of generation of hazardous and toxic wastes. Further, the recent stringent rules and regulations for safe environment are forcing materials scientists to convert these industrial toxic waste in to non-toxic and useful form and to develop novel processes for making highly value added advanced non-toxic radiation shielding materials from these wastes for broad application spectrum.
Conventional shielding materials are based on single material which is selected from either toxic lead or barium based compounds. The conventional shielding matrix contains only single phased barium based compounds, therefore posing limited radiation shielding capacity. Since brine sludge contains multiple compounds namely barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, clay, therefore I is possible to make multi compound based radiation shielding materials possessing increased radiation shielding capacity therefrom.
The application of radiation based technology is increasing day by day exponentially all over the world and this technology utilizes complete spectrum of radiations ranging from a) Far infrared b) Infra red c) Microwaves d) EMI radiations from mobiles e) X-rays f) Gamma radiation. However, the uses of radiations are associated with very well established deadly harmful effects of radiation to the human beings and therefore there is an urgent need to develop advanced radiation shielding materials preferably cost effective by utilizing waste material as the resource material for the same.
The increase in human population is forcing industrial development which is inherently associated with the drawbacks of generation of hazardous and toxic wastes. Further, the recent stringent rules and regulations for safe environment are imposing materials scientists to convert these industrial toxic wastes into non-toxic and useful form and if possible develop novel processes for making highly value added advanced non-toxic radiation shielding materials therefrom for broad application spectrum.
Brine sludge is an industrial toxic waste generated in chloral alkali industry. The chloralkali process is the main process for manufacturing of caustic soda and chlorine production all over the world. In India a total of almost 36 chloralkali plants are in operational form and Brine mud generation is around 30 kg per ton caustic soda in India, which is more than double the international average. The chloralkali plants in India date back to 1959 by Dharangadhra Chemical Works (DCW) in Tamil Nadu.
In chloralkali industry, the production of NaOH and chlorine is carried out by the electrolysis of purified brine solution i.e 30% sodium chloride solution and the process of purification of impure brine solution involves removal of sulphate and chloride salts of magnesium and potassium. Removal of sulphate species is carried out by adding barium carbonate, which is expensive and leads to the generation of toxic brine sludge waste containing barium sulphate. The removal of chloride species is carried out by adding sodium carbonate leading to the generation of brine sludge containing calcium carbonate and magnesium hydroxide. The generated brine sludge waste is dumped into landfills and the brine sludge waste contains barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, clay and toxic elements like chromium, zinc, copper and vanadium thus posing environmental threat. Therefore, there is an urgent need to convert a) toxic brine sludge waste into its non-toxic form and preferably to develop a novel process for the preparation of advanced materials while ensuring total utilization of brine sludge all over the world.
Reference may be made to the article “Characteristic change of effluent from a Chloralkali Industry of India due to process modification” by SubrataBasu et al. in International Research Journal of Environment science. 2013. vol. 2(2), pp. 44-47 wherein the use of brine sludge for making compost and fertilizer is suggested. The drawback of the article is that this application does not rule out the possibility of long term leaching out of toxic elements from the material made using brine sludge.
Reference may be made to the article “Utilization of Brine Sludge in Non-structural Building components: A Sustainable Approach” by Mridul Garg and Aakanksha Pundir in Journal of Waste Management, vol. 2014, Article ID 389316, 7 pages, wherein brine sludge has been utilized for making low value items like bricks and paver blocks using conventional cement and fly ash. However, the drawbacks of the cited process are that the brine sludge has been used in conjunction with cement and fly ash for making only paver blocks and bricks with only 35% i.e. minimal utilization of brine sludge. Thus, the problem of utilization of 65% brine sludge still remains. Further, the toxic elements present in the brine sludge have not been stabilized in cement matrix by forming any chemical linkages with the toxic elements. Hence, there is no assurance of non-leaching of the toxic elements in the environment from the prepared bricks and paver blocks. Since the brine sludge has not been converted into nano size and in functionalized form, therefore it poses limited application in making paver blocks and brick materials only. Additionally, the developed process is based on the age old concept of stabilization of industrial waste into low value added materials to somehow address the problem of disposal and utilization of waste. The process does not teach the use of any advance synthesis technology for making value added materials so as to meet the challenges and stringent rules and regulations of environmental protection Act to address the problem of utilization of industrial toxic wastes.
Reference may be made to CN101823738 where in a method for obtaining fine calcium carbonate and sodium silicate using light magnesium carbonate from chloralkali brine sludge has been reported. The drawbacks of the process are that it involves multi steps, is energy intensive and leads to the increase in pollution load as the brine sludge is not used in totality.
Reference may be made to CN101823822A, wherein hydrochloric acid is used for purifying precipitates of calcium carbonate and calcium sulphate left after the production of light magnesium carbonate. The drawbacks of the process are that it involves multi steps, is energy and equipment intensive and leads to the increase in pollution load as the brine sludge is not used in totality.
Further, from the reported prior art it is evident that total utilization of brine sludge for making highly value added advanced non-toxic radiation shielding material has not been pursued so far. From the hitherto reported prior art and based on the drawbacks of the known process, the various issues that need to be addressed and problems to be solved for ensuring total utilization of toxic brine sludge for making highly value added advanced non-toxic radiation shielding materials are summarized here as under:—                The brine sludge is toxic and therefore, it creates threat to the environment by remaining unutilized.        Crores of rupees can be saved by developing value added advanced non-toxic radiation shielding materials by a process that ensures total utilization of toxic brine sludge.        As it contains very useful and expensive precursor chemical compounds such as barium sulphate, magnesium hydroxide and calcium carbonate, therefore brine sludge can be used as a resource material and can find application in making highly value added a) advanced non-toxic radiation shielding materials b) geo polymeric materials and c) advanced chemically designed composite (ACDC) materials by utilizing unique characteristics of chemical compounds inherently present in brine sludge.        The brine sludge waste so far has limited application and that too in making low value items e g. paver block and brick materials only.        Literature reports the use of brine sludge in making fertilizers. However, it is associated with long term environmental hazards.        
Thus, keeping in view the drawbacks of the hitherto reported prior art, the inventors of the present invention realized that there exists a dire need to provide advanced non-toxic radiation shielding materials utilizing tailored brine sludge and a process that enables conversion of toxic elements like chromium, zinc, copper and vanadium present in brine sludge into non-toxic shielding phases, thereby enabling to convert a toxic waste material into highly value added advanced radiation shielding materials possessing homogeneous radiation shielding matrix.